WWII's nadir : May - October 1940

Most people consider the tense days and nights of the Blitz to be the low point of the war.

But military historians point to the period between the fall of Singapore and the fall of Tobruk as the lowest point in the war, when the huge British empire was joined by the huge Russian and American empires but the larger Allies still suffered reversal after reversal from the smaller Axis.

I think the actual moral low point was the period between the collapse of the British French front lines in May 1940 and October 1940, when it became apparent to all that the Germans had "postponed" their sea invasion of the UK.